Instrumentation: We have successfully integrated a common resonator assembly for EPRI at 10 mT and MRI at 7 T taking advantage of a common RF of 300 MHz between the two modalities. With this capability, we have developed animal handling and scanning protocols to permit sequential EPRI and MRI without having to move the object between scans. This is critical for the success of the study since the EPRI scanner and MRI scanner are at two corners of Building 10. The studies done demonstrate the feasibility of these experiments and that the images can be co-registered. Additionally MRI protocols were optimized both experimentally and computationally to derive blood flow related properties to correlate with the EPRI generated pO2 maps. A new resonator assembly is being designed to operate at 300 MHz for EPRI and at 128 MHz for MRI to permit similar studies using a 3 T MRI now available in near proximity to the EPRI scanner on the same floor. This will allow us to expand the studies since it gives additional MRI time, which is currently the limiting factor. We also completed construction of a larger size resonator for EPRI with a diameter of 7 cm which will allow us to acquire information on the feasibility of EPRI on larger sizes to learn issues related to RF heating and image fidelity. This information will be valuable in evaluating this technique for human use. This magnet was tested in the recently completed large bore size magnet/gradients and images from defined objects were successfully obtained. We have also made additional improvements in the signal acquisition system by incorporating more sensitive digitizers. In terms of acquisition software, significant improvements were made to minimize overheads in the control software making it possible to acquire images in shorter time intervals. The image reconstruction software is also optimized to handle large data sets with appropriate user interfaces so that images can be readily reconstructed immediately after acquisition so that any changes in the can conditions can be made instantly. We are now conducting routine in vivo studies on multimodality tumor imaging with longitudinal imaging capabilities allowing us to examine the same animal over a two week period and examijne the impact treatments may have on oxygenation, blood flow, metabolic status.